Notes on 2011 MBP: Uses faulty SATA port, PCIe 8x GPU.

Discussion in 'MacBook Pro' started by Anonymous Freak, Feb 28, 2011.

  1. Anonymous Freak macrumors 601

    Anonymous Freak

    Joined:
    Dec 12, 2002
    Location:
    Cascadia
    #1
    Opened up System Profiler, and noticed to oddities:
    1. The Optical drive uses the (faulty) SATA 3Gbps port, not the (good) SATA 6Gbps port.

    The hard drive does use the 6 Gbps port, although it is only a 3 Gbps device (the 750 GB drive, at least.) The optical drive is connected to a 3 Gbps port, but only connects at 1.5 Gbps (even the fastest optical drive is slower than that, so the actual link speed doesn't really matter.)

    2. The Radeon GPU is only connected via a 8-lane PCI Express connection. The chipset does have a 16-lane connection that is supposed to be for graphics cards, and the switching from onboard to discrete (according to Intel) should be fully possible using the entire 16-lane connection. The only thing I could think of is that Thunderbolt uses the other 8 lanes.
     

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  2. Hellhammer Moderator

    Hellhammer

    Staff Member

    Joined:
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    Finland
    #2
    It can't be faulty SATA port. Intel recalled all defective chipsets unless the OEM agreed not to use the defective ones. It's either fixed version or Apple limited it to 3Gb/s via firmware (there were speculation about that started by MEC and this has been done before too)
     
  3. kjos8035 macrumors member

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    Feb 28, 2011
    #3
    That's not necessarily correct.
     
  4. Anonymous Freak thread starter macrumors 601

    Anonymous Freak

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    #4
    Like I said, "Intel says" it should be possible, and "the only thing I could think of" is Thunderbolt.

    As for the faulty SATA port, that's exactly what I thought - but it decidedly says 3 Gbps, and is even listed as a separate controller, not just separate port. On my desktop, it shows the chipset as one device, with separate drives under the one chipset listing - not the two separate chipset listings.

    Correction - it shows one device for SAS chipsets, now that I look again, it does show separate chipset listings under SATA, one for each port. But in my case, it does show the full 3 Gbps for each port under Link Speed, even for connected 1.5 Gbps devices. Obviously, I don't have any other 6 Gbps-capable devices to compare against.
     
  5. xxjudgmentxx macrumors member

    Joined:
    Feb 22, 2011
    Location:
    WI
    #5
    http://www.macworld.com/article/158134/2011/02/mbp_update.html#lsrc.mod_rel

    "Earlier this year, Intel discovered problems in the chipset of Sandy Bridge processors that were shipping, but Apple vice president of worldwide Mac hardware marketing David Moody told Macworld that the company was using the latest updated versions, which corrected the flaw."
     
  6. akhbhaat macrumors regular

    Joined:
    Sep 30, 2010
    #6
    The 8x PCIe lane shouldn't bottleneck that GPU. I ran some tests with a desktop Radeon 5770 (which is more powerful than the 6750M) last summer and measured no significant difference between 16x and 8x regardless of test or conditions. 4x did produce a measurable reduction in performance but it wasn't necessarily massive.
     
  7. iBunny, Feb 28, 2011
    Last edited: Feb 28, 2011

    iBunny macrumors 65816

    Joined:
    Apr 15, 2004
    #7
    The Sandy Bridge platform, currently only has 16 available PCIe lanes. Edit: Thunderbolt conenctes via a 4x PCIe conenction. A quick google search provided me the following link http://electronicdesign.com/Content/UserStorage/14946/62390_fig3.jpg. Therefor the GPU cannot utilize the full 16 lanes as 4 are already being used, and there is no "12x" specification, so the GPU utilizes 8.

    The 8x PCIe bandwidth for the GPU should not affect performance. In very few situational circumstances would High end desktop GPU's, perhaps in multi GPU configurations see some performance increases from 8x to 16x, but in every review that I have seen its only marginal (< 5%). The Notebook version of the 6750 GPU should not see any adverse effect at all as it does not provide the fill rate or bandwidth even close to high end desktop GPUs.
     
  8. c1phr macrumors 6502

    Joined:
    Jan 8, 2011
    #8
    From what I understand on the desktop side, the only GPU's (as of the 5xxx Evergreen series on the AMD side, pre Fermi on the Nvidia side) that actually took advantage of more than 8x was dual gpu (dual GPU on the same PCB). I had this concern since my mobo only has 1 16x lane, and splits it into 2 8x's if I ever wanted to crossfire.

    I would imagine that the GPU is unaffected in this case as well then.
     
  9. KJmoon117 macrumors 6502a

    Joined:
    Jun 10, 2007
    Location:
    NC
    #9
    There's nothing faulty about the SATA port that the optical drive in the MBPs use except for that fact that it's a SATA 2 port. hyeh.
     

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